This invention relates to transmission of video signals over twisted wire pairs.
There is a present and future need to bring video signals to the desk in office environments. Rather than install new wiring or optical fiber cables, it is desirable to transmit the video signals over twisted wire pair cables which already exist in the structure and are presently used for telephone transmission, as in AT&T's Systimax.RTM. Premises Distribution System.
In applications where high resolution is required, for example, in transmitting stock quotations, it is usually necessary to transmit red, green and blue components of the video signal over separate wire pairs. However, crosstalk can be a significant problem. Further, common mode signals induced on the cable can create unacceptably high radiation emissions.
Recent proposals have suggested transmitting composite video signals over a twisted wire pair using active components to compensate for phase delays. (See, e.g., U.S. Pat. No. 5,130,793 issued to Bordry et al., and U.S. Pat. No. 5,172,413 issued to Bradley et al.) However, it should be more economical to couple video signals in a "passive" rather than an "active" manner, as described in U.S. patent application of Georger and Rutkowski, Ser. No. 07/943,644, filed Sep. 11, 1992 and assigned to the present assignee.
Transmission of red, green, and blue signals on separate twisted wire pairs has also been suggested. (See Amulet Electronics Product Literature for RGB Video Balun.) However, it does not appear that the problems of crosstalk and common mode signal suppression have been previously addressed.